摘要:

In this study two plant tissue electrodes were made by the author using a graphite base electrode modified with ferrocene and methyl blue. The tissue slices of mushroom and banana used for the source of enzyme all contain polyphenol oxidase, and results for the determination of o-diphenol are satisfactory. The linear ranges of both biosensors are 2×10−5mol/L to 3×10−2mol/L, and have more than one month's life.

ISSN:0003-2719    

DOI:10.1080/00032719308021480

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A reusable piezoelectric immunosensor has been developed for the detection of viruses and bacteria, playing an important role in acute diarrhea in early childhood. Three different methods for antibody immobilization to the gold electrode were tested. Coating the electrode with protein A gave the best results in terms of stability, sensitivity and reproducibility. Worse results were observed when coating the electrode with γ-amino propyltriethoxy silane and polyethyleneimine. Applying an antibody layer via protein A immobilization onto a 10-MHz AT-cut crystal resulted for 1 × 106to 1 × 1010virus cells and for 1 × 106to 1 × 108bacteria in a linear frequency change. The modified crystal was stable for six weeks when stored desiccated at +4°C.

ISSN:0003-2719    

DOI:10.1080/00032719308021481

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An amperometric glucose biosensor based on the oxygen electrode principle has been developed. Polycarbonate membranes (pore size from 0.01 μm to 0.4 μm) were used as external glucose diffusion membranes in order to obtain direct proportionality of the amperometric signal to the substrate concentration in the entire physiological range. The commercially available membranes - standard (hydrophilic, treated with Polyvinylpyrrolidone/(PVP)) and PVP-free membranes were compared with membranes coated with a silicone elastomer (silastic). Spindrop coating technique was used to create stable, adhesive coatings over the polycarbonate membranes. These coated membranes achieved diffusion control of the glucose flux such that the amperometric signal of the biosensor was linearly proportional to the substrate concentration up to 16 mM glucose. The membrane parameters were optimized by varying the parameters of the coating process-spin rate of the membrane rotation and the silastic/water ratio in the coating emulsion.

ISSN:0003-2719    

DOI:10.1080/00032719308021482

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The kinetic behaviour of immobilized invertase was investigated using calorimetric measurements in an enzyme thermistor device. The hydrolysis of sucrose is an exothermic process with inhibition-like kinetics above 300 mmol/1; glucose gave no measurable heat of reaction and fructose molecules are condensed in an endothermic process. The concentration dependence of the temperature signal of fructose condensation is linear up to 2 mol/1 at an optimal pH of 3.3, and the absolute value of the heat of reaction is only 25% compared with that of the hydrolytic reaction. A higher Km-value and a lower Vmaxare therefore assumed. The reaction heat of hydrolysis of sucrose decreases with increasing product concentration. A shift of the equilibrium by increasing concentrations of both products is accompanied by a competitive condensation reaction in the case of fructose. The stability of invertase in aqueous ethanol solutions was also investigated. It depends on the ethanol concentration and on the time of contact with the solvent. At 30% ethanol no inactivation within 20 min. occurs, whereas at 60% ethanol a linear dependence of the inactivation on the time of contact was found. Above 80% ethanol less than 10% enzymatic activity remained after a five-minute treatment. This irreversible inactivation has to be considered if invertase is applied in water miscible organic solvents.

ISSN:0003-2719    

DOI:10.1080/00032719308021483

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Due to the concern of stripping immobilized enzymes and antibodies from microtiter plates by the washing process, enzymelinked immunosorbent assay (ELISA) has been traditionally run on single-use, disposable units. This paper discusses the concept of stabilized, reusable ELISA plates. Antibody immobilized microtiter plates with three different modified polystyrene immobilizing surfaces were stored in Dulbecco's phosphate buffered saline/1% BSA/0.1% Thimerosal (DBT) and DBT with 3% sucrose (DBTS) for one month at 4°C. After treatment with the chaotrope and storage in buffer, the plates can be reused up to 4 times with 90% or greater antigenic capacity remaining. High and low binding microtiter plates were studied for reusability with anti-rabbit IgG (aRIgG) as a primary antibody. In each case, the procedure allowed repeated use of the same antibody immobilized plates for ELISA without re-immobilizing the antibody or loss of antigenicity. Immobilized ELISA plates were stable for one month if stored in DBTS at 4°C.

ISSN:0003-2719    

DOI:10.1080/00032719308021484

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Cyclic voltammetry has been applied for studying the cathodic reduction behaviour of 3-azo-[4-(diazin-2-yl)-benzene- sulphonamido-] -1-oxa-4-thia-spiro (4,5) decan-2-one sodium salt, as azo dye sulpha drug at the hanging mercury electrode in different supporting electrolytes, i.e. perchlorate, acetic acid-acetate buffer, nitrate and phosphate, at different pH values ranged from (1–11) and different ionic strengths (0.01–0.15). The two related compounds for the sodium salt of azo dye sulpha drug have been also studied at 0.1 M acetic acid- sodium acetate buffer (pH ∼ 3.45). Direct current stripping voltammetry (DCSV) has been used for the determination of the drug under investigation. The effect of the different parameters e.g. initial potential, scan rate, …etc. has been tested. The detection limit has been determined for azo dye salpha drug and its related compounds. Relative standard deviation at the 1 × 10−5M level was 2.9%. The method was applied to the determination of the compounds in urine sample.

ISSN:0003-2719    

DOI:10.1080/00032719308021485

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The polarographic behaviour of Aztreonam is studied. In acid media, at pH values lower than 6, in differential pulse polarography a peak is observed at a potential close to − 0.6 volts. The optimum conditions for the polarographic signal are established and the different parameters affecting the electrochemical process are studied. The relationship between peak intensity and the concentration of Aztreonam is linear for concentrations lower than 1.0 − 10−5M, the detection limit being 1.4 × 10−8M It was observed that the presence of 1-arginine does not affect the polarographic signal of Aztreonam to any significant extent.

ISSN:0003-2719    

DOI:10.1080/00032719308021486

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The simultaneous capillary GC determination of underivatized antiandrogen cyproterone acetate (CPA) and its active metabolite 15β-hydroxycyproterone acetate (OH-CPA) in spiked urine was performed on a flexible VCOT quartz capillary column, coated with a non-polar CP-Sil 5 CB liquid phase. A split/splitless injector and a flame-ionization detector were used. Equilin was used as an internal standard, and resolution of all the compounds was achieved in 6 minutes. Limit of detection was 0.04 μg/μl of injected amount for both CPA and OH-CPA, the recoveries were between 91.35% and 105.56%, and the relative standard deviation varied from 3.35% to 7.38%. The method is applicable in analysis of these steroids in biological fluids.

ISSN:0003-2719    

DOI:10.1080/00032719308021487

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A simple and rapid spectrophotometric method for the determination of seven phenothiazine derivatives has been performed either in pure form or in their dosage forms. The method is based upon the interaction of the drug in dry chloroform with bromophenol blue in the same solvent to produce a stable yellow ion-pair complex which absorbs at 410 nm, with high apparent molar absorptivity. Beer's Law is obeyed in the concentration range 1−10 ugml−1for the studied compounds. The mean recoveries range from 99.80±0.74 to 100.50±1.33. The proposed method is applied for the analysis of the studied compounds in their commercial preparations. Results are in good agreement with those obtained by official methods.

ISSN:0003-2719    

DOI:10.1080/00032719308021488

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

EDTA and DTPA complexes of terbium and europium are excited at wavelengths below 250 nm. producing the typical lanthanide emission through energy transfer from the complex to the coordinated metal. This allows determination of these rare earth ions in water without solvent extraction, the use of synergistic agents, or aromatic sensitizers. Terbium-EDTA has the most efficient energy transfer, 31%, giving a 165-fold emission enhancement and a limit of detection of 6 × 10−7M. Calibration curves are linear over a concentration range spanning three orders of magnitude. The characteristic lanthanide ion emission is obtained in all cases, but the excitation of the complexes is pH dependent, showing intensity increases up to pH 12. Mild interference by alkali and alkaline earth metals was overcome by increasing the ligand concentration, but transition metal interference was more severe. Only minor enhancement was observed at higher ligand/metal ratios.

ISSN:0003-2719    

DOI:10.1080/00032719308021489

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor